Intraoperative Localization of Metal Fragment Remained in the Human Body Using Electrical Bioimpedance: A Feasibility Study

Removal of the metal fragment remained (MFR) in the human body from bomb explosion is a surgical challenge. Although these foreign bodies sometimes cause no clinical manifestations, they may lead to a variety of complications. Localization of these MFR during surgery is usually very complicated. It requires repeated intraoperative exposure of the patient and surgical team personnel to x-ray as well as several irrelevant incisions to find the metal fragments. In this article, a noninvasive and safe impedance-based method is proposed to facilitate the identification and localization of the MFR in the body. The biological tissue and MFR buried in it were simulated in the COMSOL software using finite element method (FEM), and its identification capability was checked by measuring the electrical impedance. The bioimpedance sensor was designed and built, and the electrical bioimpedance spectrum was measured for the saline solution containing the steel ball with different diameters and at different depths. The obtained results showed that the magnitude and phase of the bioimpedance spectrum contain useful information to detect spherical steel balls in the depth of the saline solution. Also, to practically detect MFR in real tissues, steel balls with different diameters were placed in the depth of a fresh sheep meat and the bioimpedance spectrum was measured from the surface of the tissue. The results showed that the proposed method can be used as an auxiliary tool to determine the location of the MFR during surgery, therefore eliminates the need for computed tomography (CT) imaging during surgery.